Since the patent protection for Viagra in the U.S expired in 2013, a number of cheaper imitation products, some with other active ingredients , have been on the market, check here http://gulickhhc.com/erectile-dysfunction/nizagara.htm. Like Viagra, the so-called generic drugs in the USA require a prescription.In some countries, such as the UK, Switzerland and Norway, sildenafil no longer requires a prescription. However, advice from the pharmacist is sometimes a prerequisite for dispensing.